Vegetable parchment



Patent ed Apr. 9, 1935 VEGETABLE PABCHMIENT Paul Ballinger Davidson, Pittsburgh, Pa.

No Drawing. Application Apr-i130, 1932, Serial No. 608,563

6 Claims.

This invention relates to paper-making and consists in method and in product. In the prac tice of the method paper is rendered translucent, or even transparent, and given qualities and characteristics resembling those of parchment, and the product is serviceable in new fields of use.

Paper in the ordinary meaning of the word is a thin and coherent sheet of cellulose fiber. Vegetable parchment is produced by the longknown process of treating paper with sulphuric acid. The effect of the acid is to swell the fibers of cellulose to the point of producing a gelatinous mass. The process is arrested by washing with water; the gelatinous cellulose, precipitated in the still-remaining fibers of the body, acts as a cementing material; the substance of the sheet is rendered more nearly continuous; and, in consequence, the sheet manifests the properties of translucence, waterproofness, and grease-proofness which are characteristic of parchment.

The method of the present invention, unlike the sulphuric-acid method whose essential character has been indicated, does not involve chemical change nor reaction. It is, essentially, a method of impregnation, and the impregnating material is either ethyl or methyl abietate or both ethyl and methyl abietate, alone or combined with rosin oil. The abietate is dissolved in a suitable solvent and in solution is caused to penetrate the paper. After penetration the excess of solvent may be removed by drying. Among available solvents, ethylene dichloride has been found to be the best; other available solvents are acetone, toluene, and rosin spirits.

If paper be treated with such a solution of ethyl or methyl abietate with or without rosin oil, and nothing more, the treated paper will continue in an oily condition, for many purposes undesirable. The method of the invention, therefore, preferably includes in the impregnating solution, together with the ethyl or methyl abietate with or without rosin oil, either ester gum, rosin, heat-treated rosin, or sucrose octoacetate; and, if the impregnating solution be made up in such manner, the oily condition indicated willbe avoided. By heat-treated rosin is meant a rosin that has been heated to temperature suflicient to cause molecular rearrangement, with the result that crystallizing tendencies of the rosin are reduced. Incidentally, the heat treatment is generally effective to lower the acid number of the rosin, with the result that the rosin may be neutralized with smaller quantities of alkali.

The paper will by such treatment be rendered translucent, or even transparent, and parchmentlike, and that with little or no discoloration. As between the several substances named, some have a discoloring effect greater than others; and, accordingly, selection may be made between them, in cases where discoloration is not desired. The most satisfactory combination has been found to be sucrose octoacetate and methyl abietate, with ethylene dichloride as a solvent, and in the following proportions: sucrose octoacetate, 35 parts by weight; methyl abietate, 100 parts; ethyl- 10 ene dichloride, 100 parts. The solution may be prepared by dissolving the sucrose octoacetate in the ethylene dichloride, with constant stirring; and when this has been accomplished, the methyl abietate (a viscous fluid) is added and thoroughly stirred into the solution. softness in greater degree may be imparted to the product by adding to the solution a fatty acid, preferably a normally solid acid, stearic acid, for instance, or palmitic, in an amount of 5% or less by weight of the abietate.

Again, the invention may be practiced by combining in like manner the same substances, with the modification that the amount of methyl abietate is 50 parts, instead of 100, and that addition is made of rosin oil 50 parts, in place.

The ratios are given by way of example, and admit of variation through wide ranges.

The use of rosin oil has the effect of cheapening somewhat the product.

No particular type of apparatus is necessary for the application of this process to the paper; any equipment that will impregnate paper with this combination of materials and then drive off the excess of solution from the treated paper is satisfactory. In the practice of the invention the paper may be floated on the solution and the solution allowed to penetrate the paper; and, after this has been accomplished, the excess solution may be removed from the paper by means of a scraper bar or the paper may be run between squeeze rolls. The paper then is dried. Again, the invention may be practiced by spraying the solution upon the paper, or by completely immersing the paper in the solution, as is done in tub-sizing of paper. In any case the excess of solution is removed and the paper is dried. Again, the invention may be practiced by passing the untreated paper between two rolls, one of which at least carries upon its surface a layer of the solution. Satisfactory applications have been madeby passing the untreated paper between two large steel rolls, one of which revolves in a pan containing the solution and carries a layer of the solution on its surface. The paper, commentizing of the paper may in this vase be regulated by the degree to which the solution is diluted with the solvent and, to some extent, by the pressure applied to the rolls. The drying of the treated paper can be governed to a large extent by the proper selection of solvents.

If the paper upon which the method described is performed be thin and of fine texture, the resultingproduct will be translucent and may even approach transparency; if it be a heavier paper and, as such papers commonly are, of minutely irregular thickness, the translucence of the product will be correspondingly-irregular; it will present a somewhat mottled or cloudy appearance,

an appearance commonly'characteristic of true parchment.

If the paper .treated be white, the resulting product will be practically colorless; it will ordinarily be yellowed in very slight degree. It the paper be initially tinted, the color will not be changed, otherwise than by a'slight deepening of the tint.

Parchment papers produced by this new method can be written upon with pen inks and with India ink, and can be printed upon readily with printing inks. Dependent upon the kind of paper used and the condition of the component fiber, diiferent novel efiects may be produced. Delicately colored papers can be treated by this process, to produce parchment papers of like delicate coloring. This new parchment paper is an improvement over the vegeta le parchments prepared by the usual methods of reating the paper, due to the fact that there is no reaction of the parchmentizing agents with the cellulose fibers;

and, therefore, no loss of folding and tearing strength of the finished paper. This paper is highly resistant to penetration by water, and is in the class of papers termed waterproof. The

parchment papers produced by this method are more soft and pliable than the other vegetable parchment papers.

I claim as my invention:

1. A paper consisting essentially of a thin and coherent sheet of cellulose fibre containing a translucence-afiording impregnation of a substance of a group that consists of ethyl abietate and methyl abietate, and such impregnation carrying additionally an oiliness-rectifying content of a group that consists of ester gum, rosin, heattreated rosin, and sucrose octoacetate.

2. A paper consisting. essentially of a thin and coherent sheet of cellulose fibre containing a translucence-afi'ording impregnation of a ;-'substance of a group that consists of ethyl abietate and methyl abietate carried in rosin oil.

3. A body of cellulose fiber impregnated with a solution in a mutual solvent of two substances, of which substances one is of a group which consists of ethyl abietate and methyl abietate and the other of a group which consists of ester gum, rosin, heat-treated rosin, and sucrose octoacetate. v

4. Transparentized paper consisting of paper impregnated with a solution in a mutual solvent of methyl abietate and sucrose octoacetate.

5. A body of cellulose fiber impregnated with a solution in a mutual solvent of two substances, of which substances one is of a group which consists of ethyl and methyl abietates and the other is sucrose octoacetate.

6. The method herein described of treating paper which consists in impregnating the paper with a solution of a substance of a group which consists of ethyl and methyl abietates together with sucrose octoacetate in ethylene dichloride, and drying the paper.

PAUL BAILINGER DAVIDSON. 

